1. Field of the Invention
Generally, this invention relates to firearms, and bullets for firearms. More specifically, this invention relates to muzzleloading bullets with a pin at the back of the bullet for affixing a gas check thereto.
2. Related Art
This invention relates to muzzleloading bullets that have gas checks, such as the type illustrated in U.S. Pat. No. 5,458,064 (Kearns), issued Oct. 17, 1995. Kearns is incorporated herein to illustrate examples of the preferred, but not the only, structure and function of bullets with gas checks, but is not intended to limit the present invention to being applicable to only the Kearns-style embodiments. In one embodiment of Kearns, the muzzleloading bullet has a pin at its back for affixing a gas check member thereto. For this embodiment, the pin is cylindrical, and the gas check has a central, circular hole with an inside diameter slightly less than the outer diameter of the pin for frictionally engaging the pin. In this Kearns embodiment, the pin has a substantially constant diameter, and the central hole has a substantially constant diameter slightly smaller than that of the pin, so that there is contact between the pin and the hole along the whole length of the hole.
The Kearns invention has been a commercial success, and many muzzleloading bullets of its design are currently being sold. However, according to the Kearns design, if strict manufacturing tolerances are not maintained, the central hole in the gas check may be slightly oversized, relative to the pin. In this case, the bullet may be too easily separated from the gas check, and may become detached from the check in the rifle barrel, causing a possible safety hazard. Or, the central hole in the gas check may be slightly undersized, relative to that size optimum for the desired friction fit of hole around the pin. In this case, after firing, the bullet may not be separated from the gas check easily enough or at all, adversely affecting the bullet""s accuracy. In any event, there is room for improvement, even on the Kearn""s device.
According to the present invention, a muzzleloading bullet is provided with a pin at its back end for affixing a gas check thereto. The invention comprises providing a friction fit between a portion of the pin and the gas check, and providing a space between the pin and the gas check. The exploding gasses created by a gun being fired tend to deform the resilient gas check around the pin to release the pin from the gas check, and the pressure of the gasses between the gas check and the bullet surfaces tend to separate the gas check from the bullet. The space between the pin side surface and the gas check hole surface, according to the invention, reduces the surface area of contact between the pin and the hole wall compared to prior art bullets, and, therefore, there is less resistance to gas flow between the pin and the hole wall. The invented combination of friction fit and space is adapted so that the gas check separates from the bullet at the proper time (preferably, as soon after leaving the barrel as possible) and so that there is more room in the manufacturing tolerances for the fit between the pin and gas check.
Preferably, the space is at one or more positions on the pin circumference, or all the way around the pin circumference, preferably near the proximal end of the pin. This space(s) enhances the probability that gas will enter the central hole from the rear end of the gas check, flowing between the gas check and the pin, in effect, in an axial gas passage, which is enlarged as the gas deforms the gas check and pushes it away from the pin.
In a preferred embodiment, the adaptation to create the axial space between the pin and the gas check involves the pin being generally cylindrical in nature, and its distal end is larger than its proximal end, relative to the back of the bullet, resulting in a conical pin shape. In this sense, the pin shape xe2x80x9cexpandsxe2x80x9d from its proximal to its distal end as it extends out from the bullet. This way, when a suitable resilient gas check member is provided with a suitably-sized central hole for affixing the gas check to the pin, the hole of the gas check snaps over the pin, securely affixing the gas check to the back of the bullet. Also this way, because of the relative diameters of the pin and the central hole and because of the xe2x80x9cexpandingxe2x80x9d structure feature of the pin, a small space or gap exists, after the gas check is affixed to the pin, between the surface of the central hole (preferably the top inner edge of the central hole) and the outer surface of the pin near its proximal end. In the case of the generally conical pin in a generally cylindrical central hole, the xe2x80x9csmall space or gapxe2x80x9d extends all the way circumferentially around the pin. The preferred pin is enlarged (xe2x80x9cexpandedxe2x80x9d) at its distal end relative to the largest diameter of the central hole, to create a snap-on fit of the gas check on the pin.
The space/gap is important because it permits exploding gases to exit between the pin and gas check when the gun is fired, that is, it encourages exploding gases to pass from the rear of the gas check, through the central hole around the pin, to pass to the front of the gas check in between the gas check and the back of the bullet. This gas movement encourages the separation of the gas check from the bullet after firing.
Alternative embodiments of the invention provide a space or gap that does not extend circumferentially all the way around the pin. This may be done, for example, with a non-cylindrical, non-conical pin or a non-cylindrical, non-conical central hole. Many shapes of pin and central hole may be created that cooperate to temporarily hold the gas check on the pin but to also provide a space/gap between the pin and gas check to provide room for the gas flow that helps to dislodge the gas check from the pin.
While the preferred space/gap is at the proximal end of the pin (which is generally at the front end of the central hole), alternative locations may also be effective, for example, a space/gap near the middle of the axial distance between the proximal end and the distal end of the pin, or even near the distal end of the pin. As in the case of the proximally-located space/gap, such alternatively-located spaces/gaps may also work by reducing the total axial distance of frictional contact between the pin side surface and the gas check central hole surface. Thus, although the preferred embodiment places the space/gap at the proximal end of the pin, that is, downstream of the gas entry point into the central hole, alternative locations closer to the gas entry into the central hole may work. Also, the relative shapes of the pin and hole may be designed so that one or more gaps exist between the pin and the hole wall the entire length of the hole, so that exploding gasses may more easily enter the gap and then act to deform the gas check hole wall to release the gas check from the pin.
Adaptations of the pin and gas check hole may therefore comprise an axially-expanding pin such as a conical pin or an irregularly-shaped pin, and/or a conical or irregularly shaped central hole, including various combinations of these shapes. If one of either the pin member or the central hole xe2x80x9cmemberxe2x80x9d is exactly cylindrical, then the other member is preferably not exactly cylindrical, in order to create the space/gap between the two members. Because the gas check may be very thin near the central hole, the preferred central hole may also be called xe2x80x9cgenerally circularxe2x80x9d rather than cylindrical.